1. Field of the Invention
This invention relates to a liquid injection recording apparatus and a suction recovering device used in the apparatus.
2. Related Background Art
Liquid injection recording apparatus is generally called an ink jet printer and is provided with a recording head reciprocally movable along recording paper. Liquid is injected from the orifice of the recording head to form flying liquid droplets which are used to effect recording.
When bubbles mix into a liquid flow path provided in the recording head of the liquid injection recording apparatus of this type to clog the orifice at the end of the liquid flow path or the vicinity thereof, the carriage is positioned at a predetermined position which is not opposed to the recording surface, for example, a home position, and recording liquid (hereinafter referred to as ink) is sucked from the orifice portion by a suction recovering device provided on the apparatus side at said position to thereby eliminate the bubbles or the clogging.
Such a suction recovering device has a cap for covering the orifice portion of the recording head, and this cap and a pump are connected together by a tube and, by driving the pump, ink is sucked from the orifice portion by negative pressure.
In such a suction recovering device, however, the cap is designed to hermetically seal the orifice portion and therefore, during the hermetic sealing, the pressure in the cap increases to cause retraction of the meniscus of the ink in the orifice which in turn causes unsatisfactory discharge.
To eliminate such unsatisfactory discharge, ink must always be sucked in the cap, and this leads to wasting ink.
So, a cap provided with an atmosphere communicating mechanism has been proposed and a structure is adopted in which the interior of the cap is communicated with the atmosphere during the capping and the communication with the atmosphere is broken during the suction.
Even in such a structure, however, in the case of manual operation, the operator may forget to open the portion communicated with the atmosphere, and this has led to a problem that during the next capping operation, unsatisfactory discharge is caused by the retraction of the meniscus of the ink in the orifice.
In addition to such problem, in the above-described suction recovering device according to the prior art, excess ink covers and adheres to the orifice portion when ink is sucked from the orifice portion by negative pressure and during ink discharge, the presence of such adhering ink causes very unstable discharge.
It has also been proposed to provide an ink absorber in the cap and urge this absorber against the portion in which the orifice is disposed, to thereby suck and eliminate the adhering ink. However, if such a structure is adopted, there will occur the possibility of air being forced back into the orifice, which will further result in displacement of dust adhering to the absorber toward the orifice portion, which in turn will rather cause unsatisfactory discharge.
Also, the recording medium may be stained by excessive ink during the opening of the cap.
Further, in the suction recovering device, during the initial supply of ink and during the supply of ink when the ink tank has become empty, the ink suction operation positively directs the ink to the recording head side and therefore, unlike the normal discharge recovery time, a great amount of ink is sucked.
In order to increase the amount of ink sucked during such initial supply of ink, the suction pump has been of a great capacity, but this has also led to a disadvantage that the suction mechanism becomes so bulky as to prevent the device from being compact and the amount of ink sucked during the normal recording is so great as to cause wasting ink.